BELLRINGER 1/21 Copy and complete the complementary strand of DNA on a ½ sheet of paper, 1-6: G T A C C T 1. _ 2. _ 3. _ 4. _ 5. _ 6. _

Purines & Pyrimidines  A & G are Purines, they have a double ring structure.  C & T are Pyrimidines, they have a single ring structure.

SCIENTISTS WHO PROVED DNA IS HEREDITARY MATERIAL

Griffith 1928 (p. 294)  Worked with two strains of bacteria  Harmful (S-bacteria)  Non-harmful (R-bacteria )  Infected mice in 4 experiments -Harmful- Heat-killed harmful -Non-harmful - Heat killed + Non.

Results  Harmful – the mice became infected and died  Non-harmful – the mice lived  Heat-killed harmful – the mice lived  Heat killed + Non. – the mice became infected and died

Results-Griffith discovered Transformation  Disease causing strain of bacteria found in mice that died.  Transformation had occurred.

Avery -1940’s  Made extract, or juice, from heat-killed bacteria  Treated extract with enzyme that destroys lipids, proteins and carbohydrates

Avery  Treated extract with enzyme that destroys RNA  Found that transformation still took place

Avery  Treated extract with enzyme that destroys DNA  Transformation did not occur  (The mice did not get sick.)  Conclusion: DNA carries the genetic code

Hershey & Chase 1952 (p. 295)  Infected bacteria with virus called a bacteriophage  Two batches –  protein labeled with sulfur35  DNA with phosphorus-32

Hersey & Chase  Mixed radioactive viruses with bacteria  Discovered the sulfur remained with the bacteriophage and the phosphorus entered bacteria

Conclusion  All experiments showed DNA carries the genetic code!